Glass formation and structure in the system MoO3-Bi2O3-Fe2O3

The glass formation region in the MoO3-Bi2O3-Fe2O3 system was investigated by the roller-quenching method. Glasses melted at temperatures <1400 degrees C were obtained in the MoO3-rich compositions. Analysis of the glasses was made by X-ray diffraction, differential thermal analysis (DTA), infra-red spectroscopy (IR), and Mossbauer spectroscopy. According to the DTA data, the glass transformation temperature, T-g, for the different compositions varies between 360 degrees C and 440 degrees C and the crystallization temperature, T-x, is in the range 39-470 degrees C. Structural model for the glasses are suggested on the basis of IR and Mossbauer spectral data. In the region of MoO3 rich compositions, the network forming units MoO6 are connected by Mo-O-Mo bridging bonds. The presence of Me2O3 (Me=Bi, Fe) leads to transformation of MoO6 to MoO4. Thus, in a wide region of compositions the glass network has a scheelite-like structure containing isolated MoO4 structural units which are surrounded by MeO6 groups. (C) 1998 Elsevier Science B.V. All rights reserved.